Progress in psychiatric epidemiology has been dramatic. The focus on observable and experienced symptoms in the DSM definitions of mental disorder led to the development of reliable measures for use in population-based surveys. The substantial levels of comorbidity found in such efforts have forced thoughtful reconsideration of this concept. The probable role of sociocultural factors in understanding such comorbidity, however, has remained unexplored, despite evidence of the importance of the sociocultural construction of mental illness in general. The importance of the interface of culture and comorbidity was highlighted in the recently completed American Indian Service Utilization, Psychiatry Epidemiology, Risk and Protective Factors Project (Al- SUPERPFP), which included the administration of the CIDI, with cultural adaptations, to 3,084 tribal members; re-interviews of 335 participants by clinicians using the SCID; and further ethnographic interviews of 63 participants exploring distress from participants' perspectives. The most common CIDI diagnoses were Major Depressive Episode (MDE), Posttraumatic Stress Disorder (PTSD), and Alcohol Abuse and Dependence (AAD). Rates of MDE in these samples were much lower than we anticipated; however MDE was diagnosed more often in the clinical reappraisal, as was AAD. The ethnographic interviews suggested the importance of both trauma and alcohol in participants' construction of their illnesses. The specific aims are as follows: 1) To develop a framework for the investigation of sociocultural factors in diagnosis by understanding the patterns of comorbidity within the lay interview. 2) To complete in-depth analyses of those cases for which lay, clinical, and ethnographic data were collected and to develop models of sociocultural factors in the diagnostic process. 3) To use the lay interviews and clinical reappraisals to investigate how methodological factors inform our understandings of diagnostic processes. 4) To test the sociocultural models developed during the in-depth analyses, simultaneously accounting for method effects, to understand the differing perspectives of the lay interviews and clinical reappraisals of diagnosis in the context of comorbidity. This integrated psychometric, clinical, and ethnographic work is timely as we move toward DSM-V. The staff of the National Center for American Indian and Alaska Native Mental Health Research (NCAIANMHR) is uniquely qualified for this research; the team consists of anthropologists, clinicians, and psychometricians who have successfully integrated their efforts for many years. This study has important public health implications as we move towards DSM-V, both for American Indian populations but also more generally, as we seek to improve the psychiatric diagnostic process.